Fedora 11 Preview Release has been announced with a large number of new features, even more so than previous general releases. This includes Presto (delta RPM updates reducing bandwidth usage over 80% typically), automatic font and mime installer via PackageKit, Nouveau as the default driver for Nvidia cards (3D support is not mature and disabled however), simplified Anaconda text mode installation and minimal installation support, automatic Bug Reporting tool, native access to Microsoft Exchange using OpenChange, Firefox 3.1 and ThunderBird 3.0, Windows Cross Compiler (MinGW and a comprehensive set of cross compiled libraries), Ext4 as the default filesystem, experimental support for the next generation Btrfs filesystem, improved I18N with the switch to IBus input system by default, much improved Kernel Mode Support, many virtualization and security improvements, RPM 4.7, GNOME 2.26, KDE 4.2, Xfce 4.6, Linux Kernel 2.6.29, Python 2.6. GCC 4.4 and several other changes.

Well, I just ran the same test, from a -clean- slate, with apt on Ubuntu Jaunty and measured an average of 14.5 seconds on 3 runs. (Range: 13.8s - 15.0s) The total number of packages was 26701. The servers are noticeably slower right now due to the recent release of 9.04. But with apt, I'm still seeing 6 to 8 times the performance than you are seeing with yum. The fact that you seem to consider 1:28 to 2:20 good is amazing to me. (Although your numbers are about what I would have guessed for Yum.) I suppose people come to accept what they are used to. Yum *is* a lot better than it used to be.
Your numbers, while pretty poor, do show another annoying characteristic of yum in the real world. See how *variable* the performance is? Not infrequently, I have to abort and try again. And not on just one machine. This is something I have noticed about yum over time.

A. I don't have access to my Debian machine right now, but last time I did:
$ apt-get clean
$ apt-get update
... It took far more than 15 seconds. I assume that I had a lousy mirror.

B. Regarding the 1:30 time. Please note that I'm using the fastest-mirror plugin. Once I cleaned the cache (yum clean all), yum had to:
1. Rebuild the list of the fastest mirrors. (~30seconds)
2. Download the full DB's. (~1m, depends on the type of connection and the selected mirror)

C. If you disable the fastest mirror (or select the mirror by hand, like I do in Debian), you can shave ~30 seconds of this list. [1]

D. The time variation was must likely a result of different mirror (selected by fastest mirrror. ISP load variation may lead to a different mirror each time - especially given the fact that I don't have a local Fedora mirror)

E. In 95% of all cases, yum will use the cache. As you notice, yum needs <2 seconds to read and process the contents of the cache. [2]

The Fedora mirror system has lots of dud and unresponsive servers. Timeout and fall back to another server is a routine occurrence.

I fail to what yum (as product) as to do with lousy mirrors. Mind you, as I said, I've had severe issues with the local Debian mirrors.

I never *worry* or think about mirrors with apt in Ubuntu. They "just work" and work well. I only have to mess with mirror configs with yum and Fedora. Relative repo management finesse, I'm not sure about.

Sadly enough, I can't say that I share your experience.

No. I am not going to install and deinstall 100 packages on either my home desktop or on my customers' servers just to get numbers for you. I will reiterate and clarify that yum can cause swap storms on the XDMCP server in question when installing just *one* package. And I'm not the only one who has noticed. Just google for: fedora yum memory

Being a developer myself, I tend to ignore googled results.
Real numbers, from a controlled environment, is all that I trust.

P.S. I see that you're using Fedora 8. As you well know, a -lot- of work has been done to improve yum in each release, and Fedora 10 yum's performance are far better than Fedora 8's.
With presto installed, Fedora 11's yum will run circles around F10's yum, etc.